asp.net MVC 在Controller控制器中實現驗證碼輸出

using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Mvc;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Drawing;

namespace Angel.Web.Controllers
{
    public class CheckCodeController : Controller
    {
        //
        // GET: /CheckCode/

        public ActionResult Index()
        {
            this.CreateCheckCodeImage(GenerateCheckCode());
            return View();
        }

        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;

            System.Random random = new Random();
            for (int i = 0; i < 5; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                    code = (char)('0' + (char)(number % 10));
                else
                    code = (char)('A' + (char)(number % 26));

                if (code == '0' || code == 'o' || code == 'L' || code == 'I')
                {
                    i = i - 1;
                }
                else
                {
                    checkCode += code.ToString();
                }
            }

            //	Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
            Session.Contents["checkcode"] = checkCode;

            return checkCode;
        }

        private void CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return;

            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
            Graphics g = Graphics.FromImage(image);

            try
            {
                //生成隨機生成器
                Random random = new Random();

                //清空圖片背景色
                g.Clear(Color.White);

                //畫圖片的背景噪音線
                for (int i = 0; i < 25; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int y2 = random.Next(image.Height);

                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }

                Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(checkCode, font, brush, 2, 2);

                //畫圖片的前景噪音點
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);

                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }

                //畫圖片的邊框線
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }

    }
}

        /// <summary>
        /// MVC為了獲取session參數
        /// </summary>
        public override void Init()
        {
            PostAuthenticateRequest += (s, e) => HttpContext.Current.SetSessionStateBehavior(SessionStateBehavior.Required);
            base.Init();
        }

        void MvcApplication_PostAuthenticateRequest(object sender, EventArgs e)
        {
            HttpContext.Current.SetSessionStateBehavior(SessionStateBehavior.Required);
        }

Views 
html代碼
<img name="img1" id="img1" style="position:absolute;top:5px;right:36px!important;z-index:1000;" alt="單擊圖片刷新驗證碼" src="CheckCode/Index" 
onclick="JavaSccript:reloadImage('CheckCode/Index');" />
<script type="text/javascript">

function reloadImage(url) {
document.getElementById("img1").src = url + '?abc=' + Math.random();
}

   </script>